A rare heart-related health condition induced by the Covid-19 vaccine is mild and resolves quickly, according to scientists.
Myocarditis is a condition characterised by inflamed cardiac muscle and can weaken the flow of blood around the body. The most common cause is infection and in those cases it can be serious, and even fatal.
Data show that coronavirus vaccines increase the risk of a person developing myocarditis, with the risk highest in young boys and after the second dose.
A group of experts from across the US reviewed 139 cases of vaccine-induced myocarditis in people aged 12 to 20, with the average age being 16. Nine out of 10 cases were in boys and after second doses.
Of the 139 people who went to hospitals with the complaint, less than one in five were admitted to intensive care and none died.
Chest pain was an almost ubiquitous symptom, and one in three people suffered shortness of breath or fever.
“These data suggest that most cases of suspected Covid-19 vaccine-related myocarditis in people younger than 21 are mild and resolve quickly,” said Dr Dongngan Truong, the study's first author and an associate professor of paediatrics at the University of Utah.
“This study supports what we have been seeing – people identified and treated early and appropriately for Covid-19 vaccine-related myocarditis typically experience mild cases and short recovery times,” added Dr Donald Lloyd-Jones, the president of the American Heart Association.
“These findings also support the American Heart Association’s position that Covid-19 vaccines are safe, highly effective and fundamental to saving lives, protecting our families and communities against Covid-19, and ending the pandemic. Please get your child vaccinated as soon as possible.”
According to data from the UK’s Joint Committee on Vaccination and Immunisation (JCVI), for every one million Covid jabs given as a first dose to children aged 12 to 15, there are between 3 and 18 cases of myocarditis.
The risk level increases for the second dose however, to between 21 and 42 cases per million second doses.
Concern over this side effect led to the JCVI being cautious and initially not recommending under-16s get the jab, as the risk from Covid is so low.
The Chief Medical officers of the devolved administrations however ruled the wider benefits of the vaccine meant it should be rolled out, but first doses only.
However, last week the JCVI said it will start giving 12-15 year-olds a second dose, after more data emerged.